Nowadays, the convectional vertical pressurized membrane filtration systems are generally composed of a hollow fiber membrane modules provided in a vessel/tank, feed-water inlet pipes (manifolds and branch pipes), permeate outlet pipes (manifolds and branch pipes), concentrate pipes (manifolds and branch pipes) and a membrane rack. The membrane modules are connected in parallel on the two sides of the manifolds. Because of the limited filtration capacity of a single membrane module, the large system needs to use many membrane modules, which leads to system complexity, high cost and risk of fault. Furthermore the convectional pressurized membrane filtration system is not compatible with an immersion membrane filtration system.